U.S. Pat. No. 4,255,536 teaches that selected azodicarboxylates are useful to modify copolymers containing residual unsaturation.
S. S. Ivanov et at. disclose in Rubber Chem. and Tech., 30, 895 (1957) the reaction of azodicarboxylates with rubber to form branched and crosslinked derivatives.
D. S. Campbell et al., Polymer 19, 1107 (1978) and Polymer 20, 393 (1979) disclose the efficient grafting of polystyrene containing reactive azodicarboxylate units onto polydienes both in solution and in the absence of a solvent.
D. N. Schulz et al., Macromolecules 13, 1367 (1980) describe the azodicarboxylate modification of polybutadienes with respect to structure reactivity and structure property relationships.
On the other hand, the potential use of a light stabilizer containing an azodicarboxylic acid derivative to modify unsaturated elastomers and thereby incorporating the light stabilizer into the vulnerable unsaturated backbone of polymers such as ABS, impact polystyrene (IPS), high impact polystyrene (HIPS), SBS, SIS, polybutadiene (PB), polyisoprene (PI), emulsion SBR, EPDM, AES and ASA is not implied in any of the above references. The resulting polymers containing the light stabilizer exhibit greatly improved light stability.
Rubber modified polymers such as ABS and HIPS and several thermoplastics such as polypropylene (PP)/EPDM, PP/NBR, PP/NR and the like are susceptible to light induced oxidative degradation attributed mainly to the unsaturated diene phase. The instant invention locates the light stabilizer in the vulnerable diene phase through a covalent bond via the thermalene reaction of these polymers with compounds of the instant invention. The additive grafts to the polymer backbone during a reactive processing step. In addition to improved light stability, binding of the additive during processing imparts a high degree of permanence. The physical loss of stabilizer additive and migration of said additive is thus minimized during demanding end-use application. Also, non-migrating polymer-bound stabilizer additive can find use in medical and other applications requiting FDA regulation (such as in materials coming into contract with food). Thus, decreased volatility and diffusion and extraction resistance are desirable properties resulting from additives which are grafted onto a substrate.
In alloys and blends such as ABS/polycarbonate (PC), the location of the stabilizer containing a grafted hindered amine light stabilizer moiety only in the ABS phase would prevent its migration to PC where it is highly detrimental. Similar advantages could be foreseen in other polymer blends containing one or more components having unsaturated double bonds present. Examples of such polymer blends are EPDM/PP, NBR/PP, NP/PP, NR/polyphenylene oxide (PPO), emulsion SBR, ABS/nylon, ABS/PVC, ABS/polyester and the like.